Casing for a turbomachine, installation safeguard and turbomachine

ABSTRACT

Disclosed is a casing of a turbomachine which comprises at least a first casing portion comprising a first material having a first coefficient of thermal expansion and a second casing portion comprising a second material having a second coefficient of thermal expansion. The second casing portion comprises a casing structuring with flow-guiding elements and is connected in a force-fitting manner to the first casing portion by a radial press fit. Also disclosed are an installation safeguard and a turbomachine comprising the casing.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 of European Patent Application No. 15196937.5, filed Nov. 30, 2015, the entire disclosure of which is expressly incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a casing for a turbomachine, to an installation safeguard, and to a turbomachine.

2. Discussion of Background Information

Casing structurings with flow-guiding elements are often used in turbomachines, in particular in gas turbines and in the compressors thereof. A casing structuring of this type with flow-guiding elements is referred to as “Casing Treatment”, CT for short. Casing structurings have the task of increasing an aerodynamically stable operating range, in particular in compressors, through an optimization of a surge margin. An optimized surge margin allows for higher compressor pressures and therefore higher compressor loading. The disturbances responsible for a local and ultimately for the pumping of the compressor arise at casing-side ends of the rotor blades of one or more compressor stages or at the hub-side, radially internal ends of the guide vanes, since it is in these regions that the aerodynamic loading in the compressor is at its greatest. The flow in the region of the blade or vane ends is stabilized by the casing structurings.

In view of the foregoing, it would be advantageous to have available a further casing with at least one casing structuring in a turbomachine.

SUMMARY OF THE INVENTION

The present invention provides a casing of a turbomachine, which casing comprises at least a first casing portion comprising a first material having a first coefficient of thermal expansion (α₁) and a second casing portion comprising a second material having a second coefficient of thermal expansion (α₂). The second casing portion comprises a casing structuring with flow-guiding elements and is connected in a force-fitting manner to the first casing portion by a radial press fit.

In one aspect of the casing, the second coefficient of thermal expansion (α₂) may be different from the first coefficient of thermal expansion (α₁). For example, the second coefficient of thermal expansion (α₂) may be higher than the first coefficient of thermal expansion (α₁).

In another aspect of the casing, the first coefficient of thermal expansion (α₁) may be lower than or equal to 10×10⁻⁶ per Kelvin in a temperature range of from at least 20 degrees Celsius to 90 degrees Celsius and/or the second coefficient of thermal expansion (α₂) may be higher than 10×10⁻⁶ per Kelvin in a temperature range of from at least 20 degrees Celsius and 90 degrees Celsius.

In yet another aspect, the first material may be or comprise a titanium alloy and/or the second material may be or comprise a titanium alloy or a steel.

In a still further aspect of the casing, the flow-guiding elements may be integrally connected to the casing structuring and/or the second casing portion may be in one part or in one piece or may be segmented in multiple parts in circumferential direction.

In another aspect, the first casing portion may be an axially split casing portion of the casing of the turbomachine.

The present invention also provides an installation safeguard which comprises the casing as set forth above (including the various aspects thereof) and wherein the first casing portion comprises an axial delimitation for positioning the second casing portion as an installation safeguard of the second casing portion with respect to the first casing portion.

In one aspect of the safeguard, the axial delimitation may be a radial step.

In another aspect, the second casing portion may comprise at least one radially offset portion, which extends beyond the axial delimitation of the first casing portion.

The present invention also provides a turbomachine which comprises the casing set forth above (including the various aspects thereof). For example, the turbomachine may be a compressor (e.g., a high-pressure compressor), or may he an aero engine.

As set forth above, the invention proposes a casing for a turbomachine, which comprises at least a first and a second casing portion. The first casing portion comprises a first material and the second casing portion comprises a second material. The second casing portion has a casing structuring with flow-guiding elements, in particular for influencing the main flow through the turbomachine. The second casing portion is connected in a force-fitting manner to the first casing portion by means of a radial press fit. The first material has a first coefficient of thermal expansion and the second material has a second coefficient of thermal expansion.

The installation safeguard according to the invention comprises a casing according to the invention, the first casing portion having an axial delimitation, in particular a radially offset step, for positioning and for delimiting the axial displaceability of the second casing portion. The axial delimitation can similarly be an additional component which is introduced into or fixed in the first casing portion or connected to the first casing portion. A component of this type can be, for example, a ring, in particular a snap ring, which is mounted into a groove in the first casing portion and constitutes an axial delimitation for the second portion. Similarly, the additional component can be an additional ring, which is pushed into the first casing portion.

A structural axial delimitation of this type can be referred to as a “mistake proof feature”, with which it is possible to achieve a clear assignment of location or assignment of position between the first and the second casing portion. On account of the structural configuration of the second casing portion, it would then not be possible for the casing to be mounted and assembled given an incorrect or inadmissible second casing portion or second casing portion rotated through 180 degrees about a radial axis. Further casing portions, for example an axially subsequent casing portion which can be configured as a casing portion split over the circumference (as what is termed a “split case”) or as a sealing segment (as what is termed an “outer air seal”), can prevent or block installation of the second casing portion given an incorrect location or positioning of the second casing portion.

In some embodiments according to the invention, the second casing portion has at least one radially offset portion, which extends beyond the axial delimitation of the first casing portion.

The turbomachine according to the invention comprises at least one casing according to the invention. The turbomachine can be a compressor, in particular a high-pressure compressor. Similarly, the turbomachine can be an aero engine.

Advantageous further developments of the present invention are respectively the subject matter of dependent claims and embodiments.

Exemplary embodiments according to the invention can have one or more of the features specified hereinbelow.

The casing according to the invention can be designed for use in a high-pressure compressor, in a low-pressure compressor, in a high-pressure turbine or in a low-pressure turbine of an aero engine.

In a number of embodiments according to the invention, the turbomachine is an axial turbomachine, in particular a gas turbine, in particular an aero gas turbine.

In specific embodiments according to the invention, the first and/or the second casing portion do not have any components or connecting elements for connecting the first casing portion to the second casing portion. Connecting elements of this type may be screws, pins, rivets, grooves, hooks or similar elements.

In certain embodiments according to the invention, a casing portion is an axial and/or a radial portion of the casing. A portion can be referred to as a segment. A casing segmented into axial casing portions can simplify or allow for the installation of individual casing components in the casing. By way of example, flow ducts for cooling can be provided in the axial divisional plane, or casing parts segmented over the circumference can be mounted and used in a divisional plane of axially split casing portions. Furthermore, the manufacture, the assembly and the transportation of the casing can be simplified with axially split casing portions.

Materials can be metallic materials, plastics, composite materials, ceramic materials or other materials.

The term “casing structuring” as is used herein denotes a structuring or configuration of the casing or of a casing portion for influencing the main flow through the turbomachine. Casing structurings can be referred to as circulation structures or recirculation structures. Casing structurings are often used in gas turbines and in particular in compressors, for example in high-pressure compressors of aero engines. With the aid of casing structurings, it is possible to achieve or improve an aerodynamically stable operating behavior of the turbomachine. This can be achieved, for example, by what is termed optimization of a surge margin. The surge margin can be designated in simplified terms as the margin between the operating point of the turbomachine and a critical operating point with, for example, greatly unstable behavior with considerable pressure surges. At this critical operating point, it is possible, for example, for flow separation to arise at the radially outer blade or vane edge. The maximum stage pressure ratio is often achieved in a compressor stage of the turbomachine shortly before the critical operating point. The surge margin can be, for example, from about 5% to about 25%. Given a surge margin of 5%, the current operating point lies close to the critical operating point, and given a surge margin of 25% it lies correspondingly further away. With casing structurings as are proposed according to the invention, the critical operating point can be improved or shifted, such that an optimized surge margin is made possible and higher compressor pressures and therefore higher compressor loading are permitted. The flow in the region of the blade or vane ends can be stabilized by the casing structurings with flow-guiding elements.

The term “fit” as is used herein denotes a dimensional relationship between two paired, tolerance-affected parts. In particular, the two parts have the same nominal dimension. The location and size of the tolerance zones can be different. Fits or fitting systems can be standardized, for example in accordance with DEN or ISO standards. Similarly, fits or fitting systems may not be standardized. If the fits or fitting systems are not standardized, the tolerances or fit specifications for nominal dimensions can deviate from the values of the ISO standards. In particular, the fits or fitting systems deviate from the ISO standards when using non-ISO dimensional units, for example when using the length dimension “inch” instead of “meter”.

The term “press fit” as is used herein denotes a force-fitting connection of two components. The press fit can be formed by way of different diameters and/or by way of a suitable material pairing of the two components. In particular, a suitable material pairing comprises different materials with different coefficients of thermal expansion a. A press fit with different diameters can comprise components with identical or different nominal dimensions. The components can have identical or different interference fits, in addition to or as an alternative to the identical or different nominal dimensions. A press tit connects two components to one another in a force-fitting manner, such that the two components are in contact without relative movements in relation to one another.

In some embodiments according to the invention, the material of the first casing portion and the material of the second casing portion are the same. In other embodiments according to the invention, the two materials are different.

Exemplary examples for materials of the first and/or of the second casing portion are listed hereinbelow (coefficient of thermal expansion α[10⁻⁶ m/(m*K)]):

-   -   titanium alloy Ti-6A1-4V     -   (for short Ti-6-4; 6 percent by weight (% by weight) aluminum         and 4% by weight vanadium)     -   at 20 degrees (20°) Celsius (C): α=9×10⁻⁶ m/(m*K) between 20° C.         and 200° C. (20°-200°); α=9.5×10⁻⁶ m/(K)     -   titanium alloy Ti-6A1-2Sn-4Zr-2Mo (Ti-6-2-4-2; 6% by weight         aluminum, 2% by weight tin, 4% by weight zirconium, 2% by weight         molybdenum)     -   20°: α=8.5×10⁻⁶ m/(m*K)     -   20°-200°: α=9×10⁻⁶ m/(m*K)     -   stainless steel, X5CrNiCuNb17-4-4, material DIN/EN No. 1.4548,         17-4 PH®     -   20°-100°: α=10.9×10⁻⁶ m/(m*K)     -   20°-300°: α=11.1×10⁻⁶ m/(m*K)     -   stainless steel, X5CrNiCuNb15-5, material DIN/EN No. 1.4545, LW,         15-5 PH®     -   20°-200°: α=10.8×10⁻⁶ m/(m*K)     -   20°-200°: α=11.3×10⁻⁶ m/(m*K)     -   stainless steel, X12CrNiMoV12-3, material DIN/EN No. 1.4939,         Jethete M 152™     -   20°-200°: α=11×10⁻⁶ m/(m*K)     -   20°-400°: α=12×10⁻⁶ m/(m*K)     -   stainless steel, material AMS 5616 (US), ATI 418 SPL™ alloy         (Greek Ascoloy)     -   26.7°-93°: α=10.5×10⁻⁶ m/(m*K)     -   26.7°-204°: α=11×10⁻⁶ m/(m*K)     -   26.7°-427°: α=11.5×10⁻⁶ m/(m*K)     -   stainless steel, material UNS N19909, INCOLOY® 909 (UNS number:         abbreviation for “Unified Numbering System for Metals and         Alloys”)     -   20°-204°: α=8×10⁻⁶ m/(m*K)     -   20°-425°: α=7.7×10⁻⁶ m/(m*K)     -   stainless steel, G-NiCr 12 Al 6 MoNb, material DIN/EN 2.4671, IN         713C, UNS N 07713, AMS 5391     -   21°-93°: α=5.9×10⁻⁶ m/(m*K)     -   21°-204°: α=6.6×10⁻⁶ m/(m*K)     -   21°-425°: α=7.3×10⁻⁶ m/(m*K)

In principle, any material can be used for the first and second casing portion provided that the press fit is maintained over the entire intended operating range.

The coefficient of thermal expansion, abbreviated to a, can be referred to as the coefficient of thermal linear expansion. The value and the unit of the coefficient of thermal linear expansion a of, for example, 6*10⁻⁶ per Kelvin can be given as 6*10⁻⁶ m/(m*K).

In certain embodiments according to the invention, the first coefficient of thermal expansion is different to the second coefficient of thermal expansion. The first casing portion comprising the first material can have a higher or a lower coefficient of thermal expansion than the second casing portion comprising the second material. By way of example, a second casing portion comprising a material having a higher coefficient of thermal expansion than the first casing portion can have the effect that, at elevated operating temperatures, the second casing portion undergoes greater expansion than the first casing portion. This can have the effect that the force-fitting connection between the two casing portions leads to an increased force fit.

In specific embodiments according to the invention, the second coefficient of thermal expansion is lower than the first coefficient of thermal expansion.

In some embodiments according to the invention, the first coefficient of thermal expansion is lower than or equal to 10×10⁻⁶ per Kelvin in a temperature range of between at least 20 degrees Celsius and 90 degrees Celsius.

In certain embodiments according to the invention, the second coefficient of thermal expansion is higher than 10×10⁻⁶ per Kelvin in a temperature range of between at least 20 degrees Celsius and 90 degrees Celsius.

In some embodiments according to the invention, the first material is a titanium alloy and/or the second material is a titanium alloy or a steel. By way of example, both materials can be the same or different titanium alloys. In the case of different titanium alloys, the coefficients of thermal expansion can be the same or different.

In certain embodiments according to the invention, the flow-guiding elements are integrally connected to the casing structuring of the first casing portion. By way of example, the shapes or structurings of the casing structurings including the flow-guiding elements can be machined from a semifinished material, for example a disk, by a cutting process, for example by milling. Machining operations of this type can be carried out in CNC machining centers. Alternatively, the casing structurings including the flow-guiding elements can be produced by a generative process. A generative process is, for example, a laser sintering process. A generative process can be referred to as a rapid prototyping process. A further possible process for producing flow-guiding elements which are integrally connected to the casing structuring of the first casing portion is the casting process.

The first casing portion can have a different number of flow ducts (as casing structurings) and flow-guiding elements over the circumference. Purely by way of example, about 50, about 70, about 80, about 100, about 120 or another number of flow ducts and/or flow-guiding elements can be arranged over the circumference. The flow ducts and/or the flow-guiding elements can be arranged symmetrically with identical intervals to one another or asymmetrically with different intervals to one another.

In some embodiments according to the invention, the second casing portion is in one part or in one piece. A one-piece second casing portion is produced from one piece. Both a second casing portion produced in one piece from a semifinished product by a cutting process and a second casing portion produced by a generative process can be referred to as being produced in one piece. In particular, no individual parts or individual components such as, for example, flow-guiding elements are connected by means of cohesive and/or form-fitting connections to the second casing portion. Cohesive processes are, for example, welding or soldering, and form-fitting connections are, for example, screws, rivets, hooks or the like.

In specific embodiments according to the invention, the second casing portion is segmented in multiple parts in the circumferential direction. By way of example, the second casing portion can have segments with circumferential angles of about 180 degrees (two segments), about 120 degrees (three segments), about 90 degrees (four segments) or about 60 degrees (six segments). The segments can likewise have other circumferential angles. Similarly, the circumferential angles of the segments can be different, for example two segments with about 120 degrees and two segments with about 60 degrees.

In some embodiments according to the invention, the first casing portion is an axially split casing portion of the casing of the turbomachine. An axially split first casing portion can advantageously simplify the mounting of the second casing portion in that the second casing portion can be inserted into the first casing portion in the axial direction or can be connected to the first casing portion.

Some or all of the embodiments according to the invention can have one, several or all of the advantages specified above and/or hereinbelow.

By means of the casing according to the invention, it is advantageously possible to dispense with separate components or connecting elements for connecting the first casing portion to the second casing portion. It is thereby possible to realize a design which is cost-effective and simple in terms of construction and manufacturing. It is possible to constructively dispense with further connecting elements such as, for example, screws, pins, rivets or similar elements. On account of the press fit according to the invention between the first and the second casing portion, it is advantageously possible to dispense with further or alternative anti-rotation devices of the second casing portion with respect to the first casing portion. In particular, there is no need for a hook or another form-fitting anti-rotation device on the first casing portion and/or on the second casing portion in order necessary a relative movement, in particular during the intended operational use of the casing. The production costs can thereby advantageously be reduced. A hook or another component is not required if there is a press fit. Furthermore, the mounting of the second casing portion on or at the first casing portion can advantageously be embodied in simplified form, since, for example, there is no need for an exact circumferential positioning for a form-fitting connection as an anti-rotation device.

By means of the installation safeguard according to the invention for the casing according to the invention, it is advantageously possible to prevent erroneous installation through an incorrect or unintended location and positioning of the second casing portion with respect to the first casing portion. An installation safeguard can be formed by means of an axial delimitation in or on the first casing portion, in particular by means of a radially offset step.

BRIEF DESCRIPTION OF THE DRAWING

The present invention will be explained by way of example hereinbelow with reference to the appended drawing.

FIG. 1 shows a casing according to the invention of a turbomachine having a first and a second casing portion, the second casing portion having a flow-guiding element.

DETAILED DESCRIPTION OF EMBODIMENT OF THE INVENTION

The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description in combination with the drawing making apparent to those of skill in the art how the several forms of the present invention may be embodied in practice.

FIG. 1 shows a casing 100 according to the invention of a turbomachine having a first casing portion 1 and a second casing portion 3, the second casing portion 3 having a flow-guiding element 5. Furthermore, an adjustable guide vane 7, a rotor blade 9 and a main throughflow duct 11 are shown. The first casing portion 1 can be referred to as an intermediate casing (abbreviated to IMC) or intermediate casing portion. The guide vane 7 can be mounted rotatably (about a radial axis) in the intermediate casing 1.

The intermediate casing 1 is adjoined axially downstream by a further casing portion 13. Said further casing portion 13 is designed as a casing portion 13 split in the circumferential direction. FIG. 1 shows the divisional plane in which the screw connection 15 of the split casing portions is indicated. A casing, or casing portion, split in the circumferential direction can be referred to as a “split case”. In particular, the casing portion 13 is split into two casing portions 13 comprising 180 degrees, for example designed in a high-pressure compressor as a portion in a turbomachine. Instead of 180 degrees, the circumferential angles of the casing portions 13 split over the circumference can alternatively comprise 120 degrees, 90 degrees, 60 degrees, 45 degrees or another circumferential angle.

A further casing component is mounted radially on the inside of the further casing portion 13. Said further casing component is referred to in this embodiment as a sealing segment 17. The sealing segment 17 can be referred to as an “outer air seal” (abbreviated to OAS). A seal element is fastened radially on the inside of the sealing segment 17 (or is connected integrally thereto) and is referred to hereinbelow as a stripping coating 19. By means of the stripping coating 19, the gap between the radially outer end of the rotor blade 9 and the sealing segment 17 can be minimized. A casing intermediate space 21 is furthermore shown between the second casing portion 3, the further casing portion 13 and the sealing segment 17 and can be used, for example, as an air gap for cooling casing components.

With the aid of the second casing portion 3, the flow-guiding element 5 and further flow-guiding elements 5 arranged over the circumference, local flows 23 and/or circulation fields or recirculation fields are initiated. Said local flows 23 can influence critical flow fields at the outer end of the rotor blade, in that, for example, flow separation zones, fields of turbulence etc. are stabilized and a stable flow behavior is thereby produced in the turbomachine. Said behavior can be referred to as aerodynamically stable operating behavior. Particularly in the case of compressors as turbomachines, it is thereby possible to achieve optimization of the surge margin. Numerous flow-guiding elements 5 can be arranged in the second casing portion 3 over the circumference, in particular between 80 and 120 flow-guiding elements 5. The second casing portion 3 can be referred to as “casing treatment”, abbreviated to CT, or as “casing treatment ring”.

The second casing portion 3 should be securely fixed in order to achieve said effect (optimization of the surge margin) and as a whole for reliable operation of the turbomachine, and should be firmly connected to the second casing portion 1 without the risk of rotation in the circumferential direction, i.e. a relative movement between the first casing portion 1 and the second casing portion 3. According to the invention, this connection is produced by a radial press fit in the axial section A between the first casing portion 1 and the second casing portion 3. The radial press fit can be referred to as a force-fitting connection.

According to the invention, the second casing portion 3 is connected to the first casing portion 1 by means of a radial press fit within the axial section A. A force-fitting press fit can be implemented substantially by means of different diameters and/or by means of different coefficients of thermal expansion firstly of the material of the first casing portion 1 and secondly of the material of the second casing portion 3. If the two materials of the first casing portion 1 and of the second casing portion 3 are the same, e.g. on account of structural boundary conditions, the press fit is generally realized by means of different diameters. If the two materials are different, with different coefficients of thermal expansion, the press fit can be realized on account of the different coefficients of thermal expansion. In the latter case, different diameters may additionally be used.

A radial press fit according to the invention prevents rotation, i.e. a relative movement of the second casing portion 3 with respect to the first casing portion 1 during intended operational use (operating mode). The operating mode can in this case comprise all intended operating conditions with the corresponding load situations and operating temperatures. The operating temperatures may be, for example in an aero engine, 200 degrees Celsius to 300 degrees Celsius, or more.

Purely by way of example, the first casing portion 1 can be produced, for example, from a titanium alloy having a first coefficient of thermal expansion α₁ of from about 7.6×10⁻⁶ m/(m*K) to about 10×10⁻⁶ m/(m*K), or can comprise such a titanium alloy, these values relating to a temperature range of between 20 degrees Celsius and 200 degrees Celsius. A titanium alloy of this type is, for example, the material Ti-6A1-4V (titanium alloy comprising 6 percent by weight aluminum and 4 percent by weight vanadium).

Similarly purely by way of example, the second casing portion 3 can be produced, for example, from a steel alloy having a first coefficient of thermal expansion α₂ of from about 10×10⁻⁶ m/(m*K) to about 16×10⁻⁶ m/(m*K), or can comprise such a steel alloy, these values relating to a temperature range of between 20 degrees Celsius and 200 degrees Celsius.

Equally, the first casing portion 1 can comprise another titanium alloy, i.e. different from the titanium alloy Ti-6A1-4V, or can be produced therefrom. The further titanium alloy has in particular a coefficient of thermal expansion which differs from that of the titanium alloy Ti-6A1-4V.

Furthermore, the second casing portion 3 can comprise the same titanium alloy, i.e. likewise the titanium alloy Ti-6A1-4V, or can be produced therefrom. In this case, it is possible to achieve a press fit only with different diameters if the intention is to ensure a sufficient, i.e. for all intended operating states and temperatures, force-fitting connection.

In particular in the axial region A, the external diameter of the second casing portion 3 and the internal diameter of the first casing portion 1 have the same nominal diameter (given identical or different materials). The external diameter of the second casing portion 3 and the internal diameter of the first casing portion 1 may differ in terms of different fitting dimensions. En particular, both casing portions have excess dimensions.

At its front end region, on the left or upstream in FIG. 1, the second casing portion 3 has a smaller diameter compared to the diameter in the region of the press fit (axial section A). Correspondingly, at its front end region of the cutout or bore for the second casing portion 3, the first casing portion 1 likewise has a smaller diameter compared to the diameter in the region of the press fit (axial section A). A step 25 is arranged between the two diameters of the first casing portion 1. The second casing portion 3 can be pushed on in the axial direction only as far as this step 25 of the first casing portion 1. A second casing portion 3 in one part over the circumference is assumed here. The step 25 delimits the axial displacement path of the second casing portion 3. This structural embodiment of the two casing portions 1, 3 allows for installation of the second casing portion 3 only in the arrangement shown in FIG. 1. This is referred to as an installation safeguard for the second casing portion 3 in the first casing portion 1. If the second casing portion 3 is arranged in a manner rotated about 180 degrees (about the radial axis r perpendicular to the axial axis a), installation would no longer be possible, since the front end region of the second casing portion 3 with the smaller diameter would then no longer be able to be installed on account of the sealing segment 17, or would block this. This structural embodiment therefore allows for a clear assignment of location or assignment of position of the second casing portion 3 with respect to the first casing portion 1. This structural embodiment is referred to as what is termed an installation safeguard or as a “mistake proof feature”.

LIST OF REFERENCE NUMBERS

100 Casing

a Axial; axial direction

r Radial; radial direction

u Circumferential direction

A Axial section

1 First casing portion

3 Second casing portion

5 Flow-guiding element

7 Guide vane

9 Rotor blade

11 Main throughflow duct

13 Further casing portion

15 Screw connection

17 Sealing segment

19 Stripping coating

21 Casing intermediate space

23 Local flow

25 Step 

What is claimed is:
 1. A casing of a turbomachine, wherein the casing comprises at least a first casing portion comprising a first material having a first coefficient of thermal expansion (α₁) and a second casing portion comprising a second material having a second coefficient of thermal expansion (α₂), the second casing portion comprising a casing structuring with flow-guiding elements and being connected in a force-fitting manner to the first casing portion by a radial press fit.
 2. The casing of claim 1, wherein the second coefficient of thermal expansion (α₂) is different from the first coefficient of thermal expansion (α₁).
 3. The casing of claim 2, wherein the second coefficient of thermal expansion (α₂) is higher than the first coefficient of thermal expansion (α₁).
 4. The casing of claim 1, wherein the first coefficient of thermal expansion (α₁) is lower than or equal to 10×10⁻⁶ per Kelvin in a temperature range of from at least 20 degrees Celsius to 90 degrees Celsius.
 5. The casing of claim 1, wherein the second coefficient of thermal expansion (α₂) is higher than 10×10⁻⁶ per Kelvin in a temperature range of from at least 20 degrees Celsius and 90 degrees Celsius.
 6. The casing of claim 4, wherein the second coefficient of thermal expansion (α₂) is higher than 10×10⁻⁶ per Kelvin in a temperature range of from at least 20 degrees Celsius and 90 degrees Celsius.
 7. The casing of claim 1, wherein the first material is or comprises a titanium alloy.
 8. The casing of claim 1, wherein the second material is or comprises a titanium alloy or a steel.
 9. The casing of claim 8, wherein the second material is or comprises a titanium alloy or a steel.
 10. The casing of claim 1, wherein the flow-guiding elements are integrally connected to the casing structuring.
 11. The casing of claim 1, wherein the second casing portion is in one part or in one piece.
 12. The casing of claim 1, wherein the second casing portion is segmented in multiple parts in circumferential direction.
 13. The casing of claim 1, wherein the first casing portion is an axially split casing portion of the casing of the turbomachine.
 14. An installation safeguard, wherein the safeguard comprises the casing of claim 1 and wherein the first casing portion comprises an axial delimitation for positioning the second casing portion as an installation safeguard of the second casing portion with respect to the first casing portion.
 15. The installation safeguard of claim 14, wherein the axial delimitation is a radial step.
 16. The installation safeguard of claim 14, wherein the second casing portion comprises at least one radially offset portion, which extends beyond the axial delimitation of the first casing portion.
 17. A turbomachine, wherein the turbomachine comprises the casing of claim
 1. 18. The turbomachine of claim 17, wherein the turbomachine is a compressor.
 19. The turbomachine of claim 18, wherein the compressor is a high-pressure compressor.
 20. The turbomachine of claim 17, wherein the turbomachine is an aero engine. 